Language? (Dakar)

I am not yet living in Dakar, but will be in a few years. I would like to start learning either Wolof or French in order to prepare myself for Senegal. My fiance speaks a mixture of the two languages but he recommends I learn Wolof (he said its much easier). I was wondering if anyone could provide me with some feedback on what I should do. I have a hard time learning foreign languages, but i'm determined to be able to speak to my in laws without a translator.